White-Light Emission from Annealed ZnO:Si Nanocomposite Thin Films

As grown ZnO:Si nanocomposites of different compositional ratios were fabricated by thermal evaporation techniques. These films were subjected to post deposition annealing under high vacuum at a temperature of $\rm 250C^o$ for 90min. The photoluminescence (PL) spectra of annealed samples have shown marked improvements both in terms of intensity and broadening. For the first time in ZnO:Si nanocomposite films we see huge UV, red and orange peaks at 310, 570 and 640nm. Structural and Raman analysis show formation of a Zn-Si-O shell around ZnO nano clusters wherein on heating $\rm Zn_2SiO_4$ compound forms. The new emissions are due to $\rm Zn_2SiO_4$ which completes white light spectrum.Comment: 9 figure

Metal Cluster's Effect on the Optical Properties of Cesium Bromide Thin Films

Cesium Bromide films grown of glass substrates by thermal evaporation showed interesting optical properties. The UV-visible absorption spectra showed peaks which showed red shift with time. Structural and morphological studies suggested decrease in grain size with time which was unusual. Theoretical simulation shows the optical behaviour to be due to surface plasmon resonance resulting from Cesium clyindrical rods embedded in the films.Comment: 22 pages and 10 figure

Metal organic framework derived NiCo layered double hydroxide anode aggregated with biomass derived reduced graphene oxide cathode: A hybrid device configuration for supercapattery applications

Metal-organic frameworks (MOFs), due to its exceptional characteristics like high specific surface area and design diversity, serve as an outstanding sacrificial template in forming layered double hydroxides (LDHs) for highly efficient electrodes in supercapattery devices. In this work, we have prepared bimetallic layered Nickel Cobalt LDH via in-situ etching of Co-ZIF, in different Nickel concentrations directly on Ni foam that enhances the interfacial contact between substrate and the material. The optimised NiCo LDH-2 sample exhibited remarkable electrochemical behaviour with fast electrolyte ion diffusion kinetics ideal for supercapattery device and delivered a high specific capacitance of 2567 Fg−1 at 1 Ag−1. Further, the supercapattery device assembled with Ni-Co LDH as anode and rGO derived from a sustainable source as cathode demonstrated an energy density of 21 Whkg−1, power density of 0.307 kWkg−1 and good cyclic stability with capacitance retention of 88.89 % along with coulombic efficiency of 90.58 % over 1500 cycles. This work proposes an effective approach for designing layered NiCo-LDH that can be further extended to the synthesis of other transition metal-derived LDH for supercapattery devices

Recent advancement in metal-organic frameworks and composites for high-performance supercapatteries

High-performance electrochemical energy storage devices concurrently require enhanced energy density, power density, and long lifespan, which has led to the emergence of supercapattery technology. Supercapatteries are on a rapid development path with the emergence of suitable electrode materials and befitting device architecture that integrates high energy density of batteries with the high-power density and cyclability of supercapacitors in a single device. Transition metal compounds have achieved a benchmark in supercapatteries, but these compounds face challenges in controllable structure and porosity to achieve better electrochemical performance. Multifunctional metal-organic frameworks (MOFs) appear as the next-generation material and have fascinated immense consideration in supercapattery applications. Their outstanding properties like high specific surface area with controllable pore structure and architectural tunability has resulted in the advancement of active electrode materials for supercapatteries. This review critically examines the current progress in transition metal compound based electrode materials and advancement of MOF-derived structures and their composites for supercapattery applications. This review article highlights the potential in MOF-based supercapatteries that provides a blueprint for next-generation, high performance electrochemical energy storage systems